Defining Motion: Descartes, Locke and Aristotle's Act of the Able

Orientation #

He picks up from the opening of Book Three: “you see the two reasons” for taking up motion, place and time. He refers back to things “we saw earlier in the course” (Descartes on certitude and clarity; the confused as more known to us; that a line is not composed of points), and forward to Book Six, “the book on the continuous.” He stops before finishing because a student has Mass in five minutes. The previous class closed Book Two on nature acting for an end and opened Book Three on the title “natural hearing” and the need to define motion.

The class, in order #

1. Why motion, place, time in that order (“motion, place, time”) #

Point: two reasons Aristotle takes up motion and what goes with it.

1. Natural philosophy is about things that are by nature; nature is defined by motion; so it is about motion and what is connected with motion.
2. Natural philosophy is about what is common to all natural things; these (motion, place, time) are common to all natural things. Place and time come after motion because they are connected with motion, and motion is taken up before them. Aristotle speaks of place, “not space.”

• Aside: he once submitted an advanced course titled “motion, place, time”; the schedule printed it “space, time, motion,” the modern fixation, showing how ingrained custom is. Shakespeare: “Custom is a tyrant,” ruling the mind for custom’s good, not the mind’s.
• Aside on “open mind”: conclusion comes from closed; the question is what the mind is closed by. Closed by custom is bad.
• Aristotle, “second book of wisdom” [ed.: Metaphysics II]: men want you to speak as they are accustomed; anything else seems strange. Example: a college committee, each professor approaching the same thing by his discipline’s customary way. Heisenberg: going from Newtonian physics to relativity or quantum theory one may need “a new meaning of the word understanding”; a fortiori when going from physics to a poem or the soul.
• Darwin on Aristotle as biologist: Linnaeus and Cuvier “mere schoolboys compared to Aristotle.” Warren Murray: Theophrastus a lesser philosopher but a better experimental scientist than Aristotle.

2. Descartes: motion cannot be defined (“Who understands that?”) #

Point: Descartes quotes a garbled version of Aristotle’s definition and thinks Aristotle is defining what everyone already knows. Diagnosis of Descartes’ error:

1. He identifies certitude with clarity and distinctness (seen earlier in the course).
2. Perhaps by a third figure enthymeme: mathematics is more certain than other sciences; mathematics is more precise; therefore precision and certitude go together. Weak, as Aristotle’s Rhetoric example shows: “Socrates is just, Socrates is a philosopher, therefore philosophers are just” — or “Berquist is Swedish, Berquist is a philosopher, therefore philosophers are Swedish.”
3. Against this Aristotle argues in the first figure that the confused is more known to us than the distinct.
4. Descartes may also confuse clear to us with clear in itself. Example: a dry red wine — clear to me it is dry red wine, not that it is a 1956 Napa Cabernet Sauvignon; yet the latter is more determinate in the object. He confuses determination in the object with determination of our mind.
5. In fact one is surer of the confused: “What’s this table made of?” — his wastebasket looks like wood but isn’t; the more precise you try to be, the less certain you are. Two resulting mistakes:

• (a) If very sure, he thinks he knows clearly and distinctly. “I think therefore I am”: sure he thinks, but that does not mean he knows what a thought is. (The saying is not original; Augustine used it against the later skeptical academics, but did not base all his thinking on it.) Parallel: everyone is sure men and women differ; say exactly how and it gets doubtful.
• (b) Conversely, his mathematical hypotheses about nature were so clear he tended to think them true. Aside: this is partly why conspiracy theories persuade — they would be much clearer if people were deliberately betraying the country; in fact people muck through and are inconsistent. Applied to motion: we are very sure there is motion; it does not follow we know clearly what it is. If anything, sureness may be a sign we do not — as we are sure we are alive but what life is is not easy to say.

3. Rationalists and empiricists (“what is the role of experience”) #

Point: placing Descartes and Locke in the 17th–18th century landscape.

• Rationalists: Descartes, Spinoza, Leibniz — a mathematical bent, science to some extent independent of experience.
• Empiricists (from the Greek word for experience): mainly British — Bacon (near-contemporary of Shakespeare, propagandist for experimental science, “knowledge is power”), Locke, Berkeley, Hume, finally Mill — little trust in reason, wanting more experience.
• From Kant on to Einstein the question is set by these: Einstein says the whole question is the role of experience and the role of reason. The early ones are one-sided: reason independent of experience, or dependence on experience to the point of distrusting reason. There is reason to distrust reason a bit, but experience is not enough; more and more experience does not by itself yield science.

4. Locke: motion a simple idea (“simple ideas and composed ideas”) #

Point: Locke gives more of a reason than Descartes.

1. Ideas divide into simple and composed.
2. Composed ideas can be defined by their parts; simple ideas cannot.
3. Motion is a simple idea; therefore no definition of motion.

5. Not everything can or should be defined — Aristotle first (“where does the buck stop”) #

Point: the statement underlying both Descartes and Locke is Aristotle’s own, and is true; the real question is what is known without definition. Argument by regress, given three times:

• Statements. Reasoning is coming to know or guess a statement through other statements; the others must be known already. If every statement needed to be known through others, you could never begin. So some statements are known “through themselves,” i.e. not through others: knowing odd and even, no odd number is even; knowing whole and part, a whole is more than one of its parts. Knowing in the strict sense means working back to these and building up — “this marvelous thing we have in geometry”; he doubts Euclid ever had to stop, and sometimes proves things Euclid did not.
• Definitions. If every part of every definition needed defining, nothing could be defined.
• Words. Looking up a word in the dictionary gives other words; if all words were known through words you could never begin, since you come into the world knowing none. First words are learned by associating a sensed sound with a sensed thing. Example: a lost tape of his firstborn Paul in the high chair learning “cookie.” The way to learn a foreign language: tie the word to the object, not to the English word — as when he prays the Adoro te devote (visus, tactus, gustus in te fallitur [ed.: he says “decipitur”]) and thinks of his senses, not English words.
• Thomas on the Latin Averroists: “they speak as if wisdom began with them”; so Descartes and Locke, who never recall that Aristotle said this before them — either dishonesty or ignorance. Warren Murray’s joke: moderns insist on the experimental method, then make hypotheses about what the Greeks said and never test them by reading the texts. Where it stops: in the ninth book of Wisdom [ed.: Metaphysics IX] Aristotle says act cannot be defined, and we should not try to know everything by definition — yet he will use act and ability to define motion. The moderns recall the general point but not what Aristotle said was the stopping place.

6. Can a simple thing be defined? (“the point has no parts”) #

Point: definition is always a speech, never one name, and so needs a multiplicity — but the multiplicity need not be parts.

• Things with parts defined partly through parts: his definition of a Shakespearean sonnet (a likeness of thought and feeling in fourteen lines of iambic pentameter, three quatrains with alternate rhyme, completed by a couplet); “water is H₂O” — not a definition, but something.
• The geometrical point has no parts; where is the multiplicity? Answer: it may be something of another. Health is not by itself but of the body, so one can say “the good condition of the body” — not because body is a part of health but because health is of the body. Likewise “a point is the end or limit of a line”: the line is not a part of the point, but the point is something of a line. To our senses bodies are clearest; surface is the end of a body, line the end of a surface, point the end of a line. “Point” is a name; “end of a line” is a speech, signifying more distinctly.

7. Motion is something of another (“is it walking that walks?”) #

Point: motion has parts, but they are useless for defining it; its real multiplicity is being of another.

1. Motion is not simple; it is divisible, maybe forever. But a part of motion is motion, as a part of a line is a line; you cannot define a thing by itself.
2. The mathematician’s escape — a line is composed of infinitely many points — fails: a line is not composed of points, as shown earlier and to be seen again in Book Six.
3. Is motion like health and the point, something of another? Bowling: it is not rolling that rolls down the lane; walking does not walk, falling does not fall, growing does not grow — a stone falls, a man walks, a tree grows. Motion is never the thing in motion; it is always the motion of something.
4. So there is a multiplicity for a speech: say what it is of another. Locke’s “simple” does not even see that motion has parts, let alone this second multiplicity.

8. The circularity problem and the hint from act and ability (“the act of the movable”) #

Point: “of another” is not yet enough, because the obvious speech is circular.

• “Motion is something of the thing in motion” contains motion. “Motion is the act of the movable” hides the same word: what is movable? what is able to be in motion. Aristotle in dialectic examines definitions for defining a thing by itself; sometimes it is open (same word), sometimes hidden until you define the part. His example: “the sun is a star that appears by day” — sun is in the definition of day.
• Still, “motion is the act of the movable” is a true statement though circular, and it hints at act and ability: you hear act, and in movable you hear able. Three examples that motion lies between ability and act:
• In the hall he is able to be in the room, not actually; now actually — how did he get from ability to act? Motion.
• Once knee-high to a grasshopper, able to be five foot ten; now actually — growing (motion in the broader sense of change).
• Cold water on the stove is able to be hot; he does not pour until it is actually hot — a change from ability to be hot to being hot. So ability and act clearly have something to do with motion; the question is whether one can define it through them.

9. Building the definition: true but circular, then not circular but false (“coming into the room is the act”) #

Point: a definition must be both truly said of motion and not circular; he works from the room example.

1. “Coming into the room is the act of what is able to come into the room” — true (the ability to come in is actualized) but circular, like circular reasoning.
2. “Coming into the room is the act of what is able to be in the room” — not circular (defined by the end), but false: the act of the ability to be in the room is being in the room.
3. “A going from ability to act” — going is a motion; still circular. “So it’s not easy to define motion.”
4. Second thought: coming through the doorway he is partly in the room; his ability to be in the room is partly, imperfectly actualized. So “coming into the room is the imperfect act of what is able to be in the room” is true, as against being fully in the room. Like filling a glass: the glass’s ability to be full is partially realized. Student exchange: he asks whether it is too late to go on; a student has Mass in five minutes; he continues briefly, and a student asks him to repeat the question.

10. Standing in the doorway: why “insofar as it is able to be” (“the salesman with his foot in the door”) #

Point: “imperfect act” separates motion from the full act but not from a partial act that is not motion.

• Objection: stopped in the doorway (checking IDs, looking for terrorists, the salesman’s foot in the door) he is partly in the room but not coming in. So coming in must be separated both from fully being in and from standing in the doorway.
• The difference is the as such vs. by happening (accidental) distinction: it is accidental to standing in the doorway that you ever come further in; but so long as you are coming into the room you will be more in the room.
• Aristotle “kills two birds with one stone”: motion is the act of what is able to be, insofar as it is able to be. The third part brings out (i) an act that does not fully actualize the ability — it is still able to be; (ii) an act on the way to, ordered to, a further act; standing in the doorway is not as such ordered to anything further. He says one must understand “at least two things, if not three” in that third part; he names these two.
• Water: becoming hot has actualized something of the ability to be hot and will actualize more so long as it is still becoming hot; warm water taken off the heat is a partial act not on the way further — accidental that it ever becomes hot. The mother warming a baby’s bottle wants warm, not hot, and tests it on the wrist.
• Learning: “act of the ability to learn” true but circular; “act of the ability to know” not circular but seems to be knowing; so learning is the act of the ability to know insofar as one is able to know — not fully actualized and going to be actualized more. The student who drops a course knows imperfectly but is not learning; it is accidental to imperfect knowing whether you intend or ever go back. He himself knows many things imperfectly with no intention of returning, others he plans to return to.
• Asides: Monsignor Dionne visiting old students found them all where he left them, except his teacher Kasurik [ed.: ASR; probably De Koninck], who always knew more. Some are satisfied with imperfect knowing (teach with what you know and be a playboy in your spare time); others are always learning. Socrates, accused of always saying the same things about the same things: “better than always saying opposite things about the same things.”

His words #

• wisdom — his name for Aristotle’s Metaphysics (“second book of wisdom,” “ninth book of Wisdom”) [ed.: Metaphysics]
• Natural Hearing — Aristotle’s Physics (implied from previous class) [ed.: Physics]
• place, not space — Aristotle’s subject in Book IV, against the modern “space”
• third figure enthymeme — weak argument from a singular subject to a universal (“Socrates is just… therefore philosophers are just”)
• the confused is more known to us than the distinct — Aristotle’s first-figure syllogism against equating certitude with distinctness
• clear to us vs. clear (in itself) — determination of our mind vs. determination in the object
• reasoning — coming to know or guess a statement through other statements
• known through themselves — statements known not through others (odd/even, whole/part)
• act and ability — his rendering of act and potency [ed.: actus and potentia]; act cannot be defined
• speech vs. name — a definition is always a speech, signifying more distinctly than one name
• something of another — what does not exist by itself (health, point, motion) and so admits a defining speech
• circular defining — defining a thing by itself, like circular reasoning; may be hidden until a part is defined
• imperfect act — act of an ability that does not fully actualize it
• as such vs. by happening / accidental — what belongs to a thing of itself vs. what merely may happen to it
• the act of what is able to be, insofar as it is able to be — Aristotle’s definition of motion as he gives it

Texts #

Read in class

• Aristotle, Physics III, opening: the reasons for treating motion, place and time; the definition of motion.

Mentioned

• Aristotle, Physics IV (place and time); Physics VI (“the book on the continuous”)
• Aristotle, Metaphysics (“wisdom”) II, on speaking as men are accustomed; IX, on act and ability, act cannot be defined
• Aristotle, Rhetoric, third-figure enthymeme example (Socrates is just)
• Descartes (garbled quotation of Aristotle’s definition of motion; “I think therefore I am”); Augustine against the later academics
• Locke, simple and composed ideas
• Thomas Aquinas on the Latin Averroists (“as if wisdom began with them”); Adoro te devote
• Shakespeare, “Custom is a tyrant”; Heisenberg; Darwin’s letter to Aristotle’s translator; Einstein on reason and experience

His questions #

• Why does Aristotle take up place and time after motion? Because they are connected with motion, and motion is taken up before them.
• Does being very sure of something mean you know it clearly and distinctly? No — we are sure we think, are alive, that there is motion, without knowing clearly what these are.
• If every statement had to be known through other statements, would you ever know any? No; it would go on forever, so some statements are known through themselves.
• If the point has no parts, where is the multiplicity for a definition? In its being something of another: the end of a line.
• Is it rolling that rolls down the lane, walking that walks, falling that falls? No — motion is always the motion of something other than itself.
• Is “motion is the act of the movable” true? Is it a definition? True, but circular, since movable means able to be in motion.
• “Coming into the room is the act of what is able to be in the room” — is it circular? Is it true? Not circular; but false, since that act is being in the room — unless qualified as imperfect act.
• What is the difference between standing in the doorway and coming through the doorway? Standing there is only accidentally ordered further; so long as one is coming in, one will be in the room more.
• What does the third part of the definition, “insofar as it is able to be,” bring out? That the act does not fully actualize the ability and is on the way to a further act.